The navigational deflector of the alternate reality USS Enterprise open at warp

The navigational deflector (also known just as the deflector, the deflector array, the deflector dish, the main deflector, the nav deflector for short, or the parabolic dish) was a component of many starships, and was used to deflect space debris, asteroids, microscopic particles and other objects that might have collided with the ship. At warp speed the deflector was virtually indispensable for most starships as even the most minute particle could cause serious damage to a ship when it was traveling at superluminal velocities. (VOY: "Alliances", "Collective")

Ordinarily, Federation starships were equipped with a single external deflector dish. In the 2250s these devices were sometimes known as the ships' meteorite beam. (TOS: "The Cage") In the late 24th century, some starships were known to have more than one deflector. One example of this was the Intrepid-class, which had its main deflector located between the extreme forwards of decks 10 through 13, while the secondary deflector was located on the extreme forward of deck 6. (VOY: "Caretaker")

Due to its ability to project a wide variety of energies and particles, the navigational deflector was an extremely versatile piece of equipment. Many starship crews made one-time modifications to the dish to solve several problems they were facing.

Channeling such a large amount of energy through the deflector made substantial drains on the ship's power systems, notably from the warp engines. This also meant that the beam could only be fired if the ship was traveling at sublight velocities.

The deflector dish would burn out following the energy beam discharge, requiring extensive repairs, possibly replacement of the deflector altogether.

Also in 2367, the Enterprise-D's deflector was modified to amplify and reflect the subspace frequencies produced by a cosmic string fragment to change the trajectory of a group of two-dimensional beings that threatened to destroy the ship. (TNG: "The Loss")

The deflector dish fires five beams of light

In 2368, the deflector dish was modified to send five beams of light for exactly 8.3 seconds into the clouded atmosphere of Penthara IV, together with a modified phaser blast. This ionized dust particles in the planet's atmosphere, which were converted into high-energy plasma. This plasma was then absorbed by the deflector shields of the Enterprise-D and redirected into space. Warp power had to be rerouted to the deflector dish to create enough energy for the massive undertaking. (TNG: "A Matter of Time")

In three different alternate timelines, the deflector was modified to emit an inverse tachyon pulse to scan beyond the subspace barrier, this being done to ascertain the workings of an anti-time eruption. The convergence of the three tachyon pulse at the same point in space in multiple timeframes caused a paradox which created the eruption in the first instance. (TNG: "All Good Things...")

"AE-35" is a reference to 2001: A Space Odyssey, in which the AE-35 unit controls the communication dish's orientation for the Discovery.

According to illustrator John Eaves in a production featurette entitled "The Deflector Dish" included on the second disc of the Special Collector's Edition DVD of Star Trek: First Contact, the original intention was for Picard to manually reconfigure one of the ship's external weapon emplacements to eliminate the Borg beacon, but Michael Okuda advised against this tactic, contending that there would be "too much volatile equipment and materials in that area; it would destroy the ship." Okuda's concern was reflected in subsequent rewrites by having the characters take the alternate approach of detaching the dish, citing the danger.

Nevertheless, it remains unspecified in the final film as to whether the dish being "charged with antiprotons" was a normal operating condition or a result of the Borg's modifications. In "Threshold", B'Elanna Torres said the only component of the USS Voyager which generated antiprotons was its warp core, and yet such particles (presumably so generated) could also be emitted from the ship, per "The Q and the Grey". While not specified in that episode, the navigational deflector's particle emitter would seem an appropriate means of accomplishing this.

As evidenced by a call sheet from Star Trek: First Contact, live-action footage of the deflector array was filmed on Paramount Stage 15.

In "The Deflector Dish" featurette, production designer Herman Zimmerman confirmed this location, and elaborated on the set's construction: "We took the biggest stage on the lot, Stage Fifteen, and it was just barely big enough... I actually made the deflector dish about seven eighths actual size. I don't think the audience was cheated from what the size should have been, but that was a difficult thing to proportion... that whole set was made of plastic with lights inside it, and had to do a lot of different things, including separate... about twenty feet of the actual rise was done physically with the Borg actors on it, and the piece actually leaving the base that it's mounted to, and going up toward the stars."

Producer and writer Rick Berman further recalled: "I remember at first, we were pretty disappointed that we couldn't build the deflector array as big as we wanted to. There were restrictions on the size and the height that we could get up to... we were bummed out a little bit, because it wasn't as big as we wanted it to be."

During 2372 the deflector of the Defiant was modified in just ten minutes to perform as a single-shot phaser emitter when the ship was under attack from a Jem'Hadar fighter in the atmosphere of a class Jgas giant. Only one shot could be fired with this makeshift phaser emitter as it overloaded with the first shot. (DS9: "Starship Down")

The Borg "children" used a tractor beam in an attempt to steal Voyager's main deflector, to use it as an interplexing beacon for contacting the Borg. (VOY: "Collective")

Chakotay used the deflector as a "lightning rod" to stop Voyager from being fractured into different time periods by a temporal anomaly. The strike burned out the deflector dish, though Chakotay said doing so was "better than the alternative." (VOY: "Shattered")

The conceptual origins of the navigational deflector, in common with those of several other key Star Trek devices including shields, phasers, and tractor beams, can be traced to notes compiled by Gene Roddenberry through "discussion with various scientists" while writing the first pilot in 1964, and subsequently circulated among production staff, as reproduced in Roddenberry and Stephen E. Whitfield's The Making of Star Trek (p. 86): "Some kind of 'meteoroid shield' or 'meteoroid force field deflector' will be necessary in true spaceships. If not a force field, it may be a magnetic field which deflects cosmic dust or small meteoroids via an opposite charge. Or it might consist of a probing Laser beam which deflects and/or destroys dust and small particles from the path of the ship."

By the time of its third revision in April 1967, the Writers/Directors' Guide for Star Trek: The Original Series (p. 21) specified under the general heading of "DEFLECTORS" that, in addition to its deflector screen, "the ship also has 'navigational deflector beams' which, guided by 'navigational scanners', sweep out far ahead of the vessel's path through space, deflecting from the ship's course meteoroids, asteroids, or space debris and other objects which would cause damage should the vessel strike them at this enormous speed. These are all fully automated, operated by the vessel's computers."